In the general form of flying shear apparatus disclosed in the beforementioned U.S. Pat. No. 3,869,949, a shear carriage, mounting a pair of cooperating shear blades, is supported on a stationary platen. Continuously moving strip, drawn from a coil, passes through the open shear blades and is severed periodically into sheets of desired length. When it is desired to sever the strip, the shear carriage is accelerated in the direction of strip travel, until it is moving substantially synchronously therewith. At that moment, a second platen, positioned above the carriage, is actuated to close toward the lower platen, compressing the shear carriage and causing the shear blades to close and sever the work. The arrangement of the described shear is such that the shear carriage itself may be of relatively light construction, capable of being accelerated to speed in a relatively short distance. The basic shear loading, on the other hand, is developed by the heavy but stationary platens.
During the actual shearing operation, when the platens are closed onto the moving shear carriage, the heavy shearing forces are transmitted from the platens to the shear carriage by means of elongated pairs of bearing strips, which permits the carriage to continue its movement along the pass line, while the work is being sheared.
Particularly in connection with strip lines and the like where the strip is traveling at relatively high speeds, the matter of acceleration of the shear carriage to strip speed within a short distance represents a significant problem, considering the necessary mass of the shear carriage and the friction involved in sliding the carriage over the lower shear platen. Heretofore, efforts have been made to reduce the effort required to accelerate te shear carriage by utilizing antifriction roller bearings for the support of the carriage. However, such arrangements have not been satisfactory in a practical sense, because of the extremely heavy shock loading to which the carriage is subjected during the moments that the actual shearing is taking place. These severe shock loading conditions have resulted in premature failure of the antifriction bearings.
Pursuant to the invention, a novel and significantly improved arrangement is provided for a flying shear of the general type described, whereby the shear carriage is primarily supported in the planten structure by anitifriction roller bearing means, accommodating rapid acceleration and high speed travel of the carriage throughout most of its cycle of travel. Unlike the prior arrangements, however, the structure of the invention includes a novel arrangement of sliding friction bearings, in the form of pairs of elongated bearings strips arranged on the shear carriage and platens, which are inactive during the initial phases of carriage acceleration and movement, but are arranged to take the shear loading during the actual shearing operation. In this manner, the primary advantages of the roller bearing support are realized, while at the same time avoiding imposing shock loading on the bearings.
Pursunt to another and more specific feature of the invention, the shear carriage may be supported by anitifriction roller bearings means only by the upper platen, with the entire carriage being, in effect, suspended by the antifriction roller bearing means. When the shear platens are closed, as by lowering of the upper platen, the relatively broad area, sliding friction bearing elements are brought into cooperating engagement, and the roller bearings simply lift off the surfaces on which they normally run. The entire load is then taken up by the sliding friction bearings. Since, at this point in the cycle, the carriage is already moving at full speed, and the shearing operation is only momentary, the extra friction caused by the sliding bearing surfaces does not materially interfere with the desired movement of the carriage.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description and to the accompanying drawings.